The present invention relates to telecommunications networks and is by way of a development of and improvement in the telecommunications networks disclosed in my earlier UK patent application Nos. 2,291,311 (U.S. application Ser. No. 08/498,090, now allowed) and 2,291,299 (U.S. application Ser. No. 08/498,427, now U.S. Pat. No. 5,872,645) which generally relate to an Asynchronous Transfer Mode (ATM) based network system, which patent specifications are hereby incorporated by reference.
In a telecommunications network a large number of end users/customers are connected or connectable to a so-called head-end unit from which data can be received by each customer and to which data may be sent by each customer. In traditional telecommunications networks such data would be in the form of analogue voice signals and more lately in the form of digital signals.
In contrast, in the present day sophisticated network systems there is a requirement to enable data representing numerous kinds of services to be transmitted between the head-end unit and individual customers.
This requirement results in the need to accommodate high volumes of data, i.e. there is a requirement for relatively high overall bandwidth.
This requirement could theoretically be met by simply providing the network with links having the maximum data carrying capacity that is likely to be required under all operating conditions. However, such an approach would be uneconomical in that for much of the time there would be significant excess unused data carrying capacity, i.e. there would be significant redundancy in the system.
My earlier UK patent application Nos. 2,291,311 and 2,291,299 are concerned with the problem of providing capacity in the data links between the head-end unit and the large number of individual customers sufficient to satisfy the customers' requirements whilst at the same time being economical to install.
In the networks of these two earlier patent applications the architecture is designed to handle a large range of volume of customers from a few up to several thousands. This is achieved by arranging customers in groups (typically thirty-two customers) and having them share the ATM bandwidth of a common ATM pipe so that many such groups of customers can co-exist on the same system. These networks are capable of handling up to 50 Mbits of bidirectional traffic for each customer. The network disclosed in UK 2,291,311 is to a significant extent an analogue system whereas that disclosed in UK 2,291,299 is essentially a digital system.
Although both these systems go a significant way towards providing high capacity links between the individual customers and the head-end unit at an economical cost they have operational limitations which the present invention is concerned with overcoming or at least reducing.
In both of these earlier discussed networks there was no interaction between the different groups of thirty-two customers in the sense that any transmission both to and from those customers was within one stream and one stream only. This results in low power NTEs but is inefficient in its use of the network capacity. This has the effect that any broadcast service that needs to be sent to two customers on different streams resulted in two copies of the data being sent, one to each of the streams. This also limits the upstream bandwidth from the customers on one stream to the capacity of that stream only, even it there is spare capacity on one other stream.
Data travelling from the head end towards the customer is called "downstream traffic", data travelling from the customer towards the network is called "upstream traffic". There are two types of downstream traffic namely, point to point traffic which goes to one customer only and broadcast traffic which can go to many customers. There is only point to point traffic in upstream traffic.
In the previous systems as disclosed in UK 2,291,311 and UK 2,291,299 the customer's equipment only looked for their own point to point traffic and any broadcast channels they wanted from their own stream. Likewise they could only transmit data upstream on their stream after they had negotiated with the head-end to send a cell on that stream.